Wireless local area networks (LANs) provide Internet access in hard-to-wire places such as airports, malls, and theaters. Due to the physically open and uncontrolled nature of the communications medium, e.g., radio frequency electromagnetic radiation, security is a concern. One of the existing standards for wireless LANs is a standard approved by the Institute of Electrical and Electronic Engineers (IEEE), commonly referred to as IEEE 802.11. This standard provides specifications related to access security, e.g., authentication and encryption.
Networks conforming to the IEEE 802.11 standard, referred to as 802.11 networks, typically comprise mobile nodes (MNs), such as personal computers (PCs) or personal digital assistants (PDAs). These MNs gain access to the 802.11 network via an Access Point (AP). An AP provides communication between a MN in a wireless LAN and another MN in the same or another LAN. In accordance with the IEEE 802.11 standard, before a MN can access the network, (1) it must be authenticated to verify its access privileges, and (2) a security association in the form of a shared secret key must be established between the AP and the MN. The AP and the MN use this key to encrypt all data communications between the AP and the MN. However, there are several disadvantages associated with the current IEEE 802.11 authentication and encryption schemes. First, the current authentication protocol for 802.11 networks specifies a shared key authentication method, wherein the AP and the MN are previously (prior to attempted communications) provided with the same shared secret key, to realize the mechanism for the AP to grant authentication and association to a specific MN. This typically requires that the secret key be delivered to the MN via a secure channel or mechanism independent of the 802.11 network.
Another disadvantage is that the same shared key used for authentication is also used for encryption. This requires that each time a new MN is added or an existing MN leaves the trusted, shared relationship, the key must be changed and delivered reliably to each MN. This makes the authentication scheme cumbersome and unsuitable for public networks, which typically require per user, per session keys.
Along with authentication requirements at the initial connection between the MN and the AP (commonly referred to as the data link layer or layer-2), there are authentication requirements at higher levels, such as on the network layer (layer-3). It is not uncommon for a user to carry a mobile device across multiple LANs with different network addresses. In accordance with the IEEE 802.11 standard, this roaming ability also requires an authentication routine to be executed between the MN and each AP encountered. As currently contemplated, the aforementioned data link layer and network layer authentication schemes are separately employed and utilize different algorithms and authentication information. This dual process is inherently inefficient and slows the authentication process. An improved scheme for authentication and key exchange is desired.